Sensorless control device for synchronous electric motor

ABSTRACT

The invention provides a synchronous motor sensorless controller which drives a synchronous motor without use of a rotational position sensor. The controller has a relative position counter  4  which acquires an estimated position of a magnetic pole from the position-and-speed estimation device simultaneously with resetting a summated value to zero when the reference position signal is input and which starts summation operation; and a speed instruction generator  3  having a position controller  29  which performs position control operation on the basis of a deviation between an instruction value pertaining to the amount of movement from the reference position and a summated value output as a relative position from the relative position counter, the generator outputting a speed instruction. The sensorless controller can position at a predetermined location a synchronous motor not having a position sensor.

TECHNICAL FIELD

This invention relates to a sensorless controller of a synchronous motorwhich performs positioning operation by utilization of a limit switch.

BACKGROUND ART

Many automatic warehouses, transfer machines, and machine tools areconstructed so as to position a predetermined object at a predeterminedposition while a motor is used as a power source. Generally, two limitswitches are used for positioning and are arranged in a specific manner;namely, a desired rotational speed is switched to a low rotational speed(e.g., a creep speed) in accordance with a signal output from a firstlimit switch provided at a deceleration start position, thusdecelerating the motor. While the motor is in this decelerated state,the object is transported to a predetermined position. When the objecthas reached a predetermined position, the rotation of the motor isstopped in accordance with a signal output from the second limit switchprovided at a stop operation start position.

FIG. 11 is a view showing various waveforms produced in conjunction witha simplified positioning method utilizing a limit switch in adeceleration circuit of a related-art motor described in, e.g.,JP-A-60-223486. FIG. 11A is a waveform of a target speed; FIG. 11B is awaveform of a voltage output from a charge-and-discharge circuit; FIG.11C is a waveform of a deceleration timing signal; and FIG. 11D is awaveform of a speed instruction.

In the drawings, reference symbol “a” designates a first limit switchprovided at a deceleration start position; “b” designates a second limitswitch provided at a stop operation start position; “v1” designates avoltage signal used for determining a deceleration timing; and “t”designates a time which lapses from input of a deceleration instructionuntil switching of a target rotational speed to a low speed.

Simplified positioning operation utilizing a limit switch provided in adeceleration circuit of a related-art motor will now be described byreference to FIG. 11.

When an object has passed by the first limit switch “a” provided at thedeceleration start position while being transported at high speed (ormedium speed), the charge-and-discharge circuit performs sequentialelectrical discharge of an output voltage in accordance with a signaloutput from the limit switch “a” and with a voltage signal correspondingto a desired rotational speed. When the voltage output from thecharge-and-discharge circuit has dropped to a voltage signal v1 (FIG.11B), a deceleration timing signal changes from H to L (FIG. 11C),thereby switching a target speed from high speed (or medium speed) tolow speed (FIG. 11A).

Deceleration operation is started in accordance with a speed instructionat the switching timing of the target speed. When the object has passedby the second limit switch “b” provided at the stop operation startposition while being transported at low speed after having completeddeceleration, the speed instruction is set to 0, thus halting rotationof the motor (FIG. 11D).

A sensorless controller which controls an induction motor whose actualposition information is unknown for reasons of “slippage” of the motorgenerally performs the above-described simplified positioning operationinvolving usage of the limit switch.

In contrast, a permanent magnet synchronous motor—which is moreefficient, smaller, and easier to control than an induction motor andhas become prevalent in the industry—requires current controlcorresponding to the position of a rotor for controlling torque. Since aposition sensor, such as an encoder or resolver, is usually used,positioning of the synchronous motor is usually controlled by use of theposition sensor.

If the position sensor can be removed, realization of a more compact,lighter-weight, and less-expensive motor and improvements in environmentresistance and reliability can be achieved. Hence, research on varioussensorless control of position is pursued.

JP-T-8-505996 describes a method for controlling an observer base of apermanent magnet synchronous motor as an example of related-artposition-sensor-less control operation. Under this method, the positionand speed of a rotor of a multi-phase brushless permanent magnetsynchronous motor are controlled with high resolution. The values ofposition and speed of the rotor estimated by use of a measured statorphase current are used for desired adjustment of the position or speedof the rotor. Alternatively, the amount of voltage to be applied torespective stator phases is determined for issuing an instruction to therotor such that the rotor follows a desired trace of position or speed.

Estimation of a position of the rotor to be performed in the case ofsensorless control of the synchronous motor is for detecting theposition of the motor within a cycle of electrical angle; that is, theposition of a magnetic pole. Since the mechanical position of a shaft ofthe motor (i.e., a mechanical angle of the motor) is unknown (e.g., anelectrical angle of a four-pole motor rotates twice within one cycle ofthe motor; that is, one cycle of a mechanical angle), controlling amechanical position requires use of a contrivance. Moreover, when asynchronous motor is subjected to sensorless control, positions ofmagnetic poles are estimated by means of an electrical current flowingthrough the motor. Hence, when flow of an electric current isinterrupted by stopping operation of a drive circuit when the motor isnonoperational, positions of magnetic poles cannot be estimated. If theshaft of the motor is rotated in this situation, there will arise aproblem of positions of the magnetic poles being lost.

As mentioned above, sensorless positional control of the synchronousmotor is difficult, and driving of a sensorless synchronous motor isusually employed for controlling a speed.

[Problems that the Invention is to Solve]

As mentioned above, the simplified positioning that is commonly employedby an induction motor and uses a limit switch requires two limitswitches; that is, a limit switch to be used for starting decelerationoperation, and another limit switch to be used for stopping operation.Moreover, the simplified positioning also presents a problem ofcomplicated operation, such as positional adjustment of limit switches.

When a synchronous motor is to perform positioning control operation,the motor must be equipped with position sensors, thus adding to cost.

The invention has been conceived to solve such a problem, and a firstobject of the invention is to obtain a sensorless controller of asynchronous motor which positions a synchronous motor at a desiredlocation without use of a sensor.

A second object of the invention is to obtain a sensorless controller ofa synchronous motor which enables a reduction in the number of limitswitches to be provided and facilitates adjustment of setting of thelimit switches.

DISCLOSURE OF THE INVENTION

A synchronous motor sensorless controller of the invention includes acurrent sensor for detecting an electric current of a synchronous motor,a position-and-speed estimation device for computing an estimated speedof the synchronous motor and an estimated position of a magnetic polethrough use of the current output from the current sensor, and a speedcontroller for controlling speed of the synchronous motor through use ofa speed instruction and the estimated speed; and drives the synchronousmotor without use of a rotational position sensor. The controllercomprises reference position signal output means for outputting areference position signal serving as a standard for positioning countingoperation; a relative position counter which acquires an estimatedposition of a magnetic pole from the position-and-speed estimationdevice as a reference position simultaneously with resetting a summatedvalue to zero when the reference position signal is input and whichstarts summation operation; and a speed instruction generator having aposition controller which performs position control operation on thebasis of a deviation between an instruction value pertaining to theamount of movement from the reference position and a summated valueoutput as a relative position from the relative position counter, thegenerator outputting a speed instruction. Therefore, a synchronous motornot having a position sensor can be positioned at a predeterminedlocation. Further, there can be obtained a sensorless controller of asynchronous motor which enables a reduction in the number of limitswitches to be placed and facilitates adjustment of setting of limitswitches.

The speed instruction generator is arranged to enable setting of adeceleration start position and a stop operation start position, startdeceleration operation when a summated value output as a relativeposition from the relative position counter has reached the decelerationstart position, and start stop operation when the summated value hasreached the stop operation start position. Therefore, two limitswitches; that is, a limit switch to be used for starting decelerationoperation and another limit switch to be used for starting stopoperation, both having hitherto been required to control positioningoperation, can be embodied as a single limit switch. Moreover, a stopposition can be readily adjusted by changing the deceleration startposition or the stop operation start position. Consequently, acomplicated operation, such as adjustment of a stop position byre-setting of limit switches which would have hitherto been required,can be obviated.

Further, the speed instruction generator can set at least two pairs,each pair formed from a deceleration start position and a stop operationstart position, enables selection of one to be used during operationfrom the deceleration start position and the stop operation startposition, starts deceleration when a summated value output as a relativeposition from the relative position counter has reached a selecteddeceleration start position, and starts stop operation when the summatedvalue has reached a selected stop operation start position. Therefore,positioning can be performed in two or more types of patterns withoutinvolvement of an increase in the number of limit switches. Further, anoperation for adjusting limit switches or changing the decelerationstart position is obviated even at the time of switching of apositioning pattern.

In addition, a synchronous motor sensorless controller includes acurrent sensor for detecting an electric current of a synchronous motor,a position-and-speed estimation device for computing an estimated speedof the synchronous motor and an estimated position of a magnetic polethrough use of the current output from the current sensor, and a speedcontroller for controlling speed of the synchronous motor through use ofa speed instruction and the estimated speed; and drives the synchronousmotor without use of a rotational position sensor. The controllercomprises reference position signal output means for outputting areference position signal serving as a standard for positioning countingoperation; a relative position counter which acquires an estimatedposition of a magnetic pole from the position-and-speed estimationdevice simultaneously with resetting a summated value to zero when thereference position signal is input and which starts summation operation;speed instruction change position signal output means for outputting aspeed instruction change position signal; and a speed instructiongenerator having a position controller which performs position controloperation on the basis of a deviation between an instruction valuepertaining to the amount of movement from the reference position and asummated value output as a relative position from the relative positioncounter, the generator outputting a speed instruction. Therefore, asynchronous motor not having a position sensor can be positioned at apredetermined location.

Further, the speed instruction generator enables setting of adeceleration start position, starts deceleration operation when asummated value output as a relative position from the relative positioncounter has reached the deceleration start position, and starts stopoperation when the summated value has reached the stop operation startposition. The accuracy of stoppage of a synchronous motor not having aposition sensor at a predetermined location can be improved further byoutputting a reference position signal during low speed operation.

The speed instruction generator enables setting of a deceleration startposition, a first operation change relative position, and a secondoperation change relative position; changes a speed instruction when asummated value output as a relative position from the relative positioncounter has reached the first operation change relative position or thesecond operation change relative position; starts deceleration when asummated value output from the relative position counter as a relativeposition has reached the deceleration start position; and starts stopoperation when a speed instruction change position signal is outputtedfrom the speed instruction change position signal output means.Therefore, a synchronous motor not having a position sensor can bepositioned at a predetermined location, and the speed of the motor ischanged during the course of operation over a distance between the firstoperation change relative position and the second operation changerelative position, whereby the distance can be used for inspection orthe like.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a view showing the configuration of a sensorless controller 1a of a synchronous motor according to a first embodiment of theinvention;

FIG. 2 is a view showing the configuration of a speed instructiongenerator 3 provided in the sensorless controller 1 a of the synchronousmotor according to the first embodiment of the invention;

FIG. 3 is a view showing the configuration of a sensorless controller 1b of a synchronous motor according to a second embodiment of theinvention;

FIG. 4 is a view for describing operation of the sensorless controller 1b of the synchronous motor according to the second embodiment of theinvention;

FIG. 5 is a view showing the configuration of a sensorless controller 1c of a synchronous motor according to a third embodiment of theinvention;

FIG. 6 is a view for describing operations of the sensorless controller1 c of the synchronous motor of the third embodiment of the invention,the operations differing because of a difference in rotationaldirection;

FIG. 7 is a view showing the configuration of a sensorless controller 1d of a synchronous motor according to a fourth embodiment of theinvention;

FIG. 8 is a view for describing the operation of the sensorlesscontroller 1 d of the synchronous motor of the fourth embodiment of theinvention;

FIG. 9 is a view showing the configuration of a sensorless controller 1e of a synchronous motor according to a fifth embodiment of theinvention;

FIG. 10 is a view for describing the operation of the sensorlesscontroller 1 e of the synchronous motor of the fifth embodiment of theinvention; and

FIG. 11 is a view showing various waveforms produced in conjunction witha simplified positioning method which utilizes a limit switch providedin a deceleration circuit of a related-art motor described in, e.g.,JP-A-60-223486.

BEST MODES FOR CARRYING OUT THE INVENTION

First Embodiment

FIG. 1 is a view showing the configuration of a sensorless controller 1a of a synchronous motor according to a first embodiment of theinvention. In the drawing, reference numeral 1 a designates a sensorlesscontroller of a synchronous motor; 2 designates a sensorless speedcontrol section; 3 designates a speed instruction generator; 4designates a relative position counter; 5 designates an external deviceserving as reference position signal output means, the means outputtinga reference position signal serving as a standard for a positioningcount; and 10 designates a synchronous motor.

Further, reference numeral 20 designates a subtracter for computing adifference between a speed instruction output from the speed instructiongenerator 3 and an estimated speed output from a position-and-speedestimation device 27 to be described later; 21 designates a speedcontroller for outputting a current instruction in accordance with anoutput from the subtracter 20; 22 designates a subtracter for computinga difference between a current instruction output from the speedcontroller 21 and the output from a current coordinate converter 26 tobe described later; 23 designates a current controller outputting avoltage in accordance with an output from the subtracter 22; 24designates a voltage coordinate converter for converting an output fromthe current controller 23 into a voltage to be applied to thesynchronous motor 10 through coordinate conversion; 25 designates acurrent sensor; 26 designates a current coordinate converter forconverting an output current detected by the current sensor 25 intocoordinates; and 27 designates a position-and-speed estimation devicefor estimating the position and speed of the synchronous motor 10through use of the current output from the current coordinate converter20 and the voltage output from the current controller 23.

The sensorless speed control section 2 is basically identical inconfiguration with a method for controlling a synchronous motor withoutuse of a sensor, the motor being operative over an entire speed range,which is proposed as, e.g., “CONTROL OF SENSORLESS SALIENT-POLE PMSYNCHRONOUS MOTOR OVER ENTIRE SPEED RANGE,” pp. 240 to 247, No. 2, Vol.120, Transactions D of The Institute of Electrical Engineers of Japan,2000 or a method proposed as, e.g., “SENSORLESS CONTROL OF POSITION OFBRUSHLESS DC MOTOR USING ADAPTIVE OBSERVER,” pp. 579 to 586, Vol. 113,Transactions D of The Institute of Electrical Engineers of Japan, 1993.

Operation of the sensorless speed control section 2 will now bedescribed.

The subtracter 20 computes a difference between a speed instructionoutput from the speed instruction generator 3 and an estimated speedoutput from the position-and-speed estimation device 27.

The speed controller 21 computes and outputs a current instruction onthe basis of a speed deviation signal which is generated by, e.g., aproportional element and an integral element and is output from thesubtracter 20.

The subtracter 22 computes a difference between a current instructionoutput from the speed controller 21 and a current value output from thecurrent coordinate converter 26.

The current controller 23 computes and outputs a voltage instruction onthe basis of a current deviation signal which is generated by, e.g., aproportional element and an integral element and is output from thesubtracter 22.

The voltage coordinate converter 24 converts a voltage instructionoutput from the current controller 23 into a voltage to be applied tothe synchronous motor 10 through use of an estimated position outputfrom the position-and-speed estimation device 27.

The current coordinate converter 26 converts a current of thesynchronous motor 10 into coordinates through use of an estimatedposition output from the position-and-speed estimation device 27.

The position-and-speed estimation device 27 estimates the position andspeed of the synchronous motor 10 from a voltage output from the currentcontroller 23 and a current output from the current coordinate converter26.

In the sensorless controller 1 a of the synchronous motor of the firstembodiment, the sensorless speed control section 2 is connected to therelative position counter 4, and the position-and-speed estimationdevice 27 estimates the position of a magnetic pole obtained when areference position signal is input from the external device 5 (i.e.,information about an electrical angle of the motor). The thus-estimatedposition value is output to the relative position counter 4 as amagnetic pole position serving as a standard. The estimated positionvalue is output to the relative position counter 4 every time a magneticpole passes by the magnetic pole position serving as a standard.

FIG. 2 is a view showing the configuration of the speed instructiongenerator 3 provided in the sensorless controller 1 a of a synchronousmotor according to the first embodiment of the invention. In theillustration, reference numeral 28 designates a subtracter for computinga difference between an instructed amount of movement from the referenceposition and a position relative to the standard position output fromthe relative position counter 4; and 29 designates a positioncontroller.

By reference to FIGS. 1 and 2, operation of the sensorless controller 1a of the synchronous motor of the first embodiment will now bedescribed. The sensorless controller 1 a of the synchronous motor thatdoes not use any sensor for sensing an absolute position computes anabsolute position by determining a position relative to a referenceposition while the position of a magnetic pole obtained when a referenceposition signal is input is taken as a reference position.

When the reference position signal is input from the external device 5,the relative position counter 4 resets a total value to zero.Simultaneously, the relative position counter 4 starts summation ofposition values of a magnetic pole while the position of the magneticpole obtained when a reference position signal has been input is inputas a reference position from the sensorless speed control section 2.

The relative position counter 4 determines a position relative to thereference position, by means of adding up a value counted every time themagnetic pole passes by a magnetic pole position serving as a standardfor counting and the amount of displacement from a reference positionfor a magnetic pole within one cycle of an electrical angle.

The speed instruction generator 3 is arranged such that the positioncontroller 29 prepares a speed instruction on the basis of a differencebetween an instructed amount of movement from the reference positiondetermined by the subtracter 28 and a position relative to the referenceposition output from the relative position counter 4. The speedinstruction generator 3 can change a speed instruction in accordancewith information about the relative position output from the relativeposition counter 4, thereby enabling position control operation.

In the sensorless controller 1 a of the synchronous motor of the firstembodiment, the relative position counter 4 adds up a value countedevery time a magnetic pole passes by a magnetic pole position serving asa reference and the amount of displacement from the reference positionfor a magnetic pole within one cycle of an electrical angle, therebydetermining a position relative to the reference position. Hence, asynchronous motor not having a position sensor can stop an object at aposition relative to the reference position. Further, a position sensorhas hitherto been used when a synchronous motor performs positioningoperation. However, a synchronous motor can perform positioningoperation without use of a position sensor, thereby curtailing cost of asystem while improving reliability.

Second Embodiment

FIG. 3 is a view showing the configuration of a sensorless controller 1b of a synchronous motor according to a second embodiment of theinvention. In the drawing, reference numerals 2, 4, and 10 designatethose elements which are identical with those shown in FIG. 1, and theirrepeated explanations are omitted. Reference numeral 1 b designates asensorless controller of a synchronous motor; 6 designates a limitswitch which outputs a reference position signal to the relativeposition counter 4; and 7 a designates a speed instruction generator forchanging a speed instruction in accordance with an output from therelative position counter 4. Further, reference symbols X1, X2 designatereference values set in advance for the speed instruction generator 7 a.Here, X1 corresponds to the first limit switch “a” provided at thedeceleration start position in FIG. 11 and designates a distance betweena position at which the limit switch 6 is to output a reference positionsignal and the deceleration start position. X2 designates corresponds tothe second limit switch “b” provided at the stop operation startposition shown in FIG. 11 and designates a distance between a positionat which the limit switch 6 is to output a reference position signal andthe stop operation start position.

FIG. 4 is a view for describing operation of the sensorless controller 1b of the synchronous motor according to the second embodiment of theinvention. FIG. 4A shows an example configuration of a transferapparatus; FIG. 4B shows a speed instruction output from the speedinstruction generator 7 a; FIG. 4C shows an output from the relativeposition counter 4; and FIG. 4D designates a speed. In the drawing,reference numeral 1 b designates a sensorless controller of asynchronous motor capable of inputting a signal output from the limitswitch 6; 10 designates a synchronous motor; 11 designates a shaft ofthe synchronous motor; 12 designates a belt which is connected to theshaft 11 of the synchronous motor and is actuated; 13 designates anobject which is transported while being secured to the belt; and 14 adesignates a stopper.

Operation of the sensorless controller 1 b of the synchronous motor ofthe second embodiment will now be described by reference to FIGS. 3 and4.

When the object 13 passes by the limit switch 6 while being transportedin a rightward direction from the left end of FIG. 4A, the limit switch6 outputs a reference position signal.

Upon receipt of a reference position signal output from the limit switch6, the relative position counter 4 resets a total value to zero.Simultaneously, the relative position counter 4 starts summation ofposition values of a magnetic pole while the position of the magneticpole obtained when a reference position signal has been input is inputas a reference position from the sensorless speed control section 2.

The relative position counter 4 determines a position relative to thereference position, by means of adding up a value counted every time themagnetic pole passes by a magnetic pole position serving as a standardfor counting and the amount of displacement from a reference positionfor a magnetic pole within one cycle of an electrical angle. A valuesummated by the relative position counter 4 increases in a manner shownin FIG. 4C.

When the value counted by the relative position counter 4 has reached apreviously-set deceleration start position X1 as shown in FIG. 4C, thespeed instruction generator 7 a starts deceleration operation bychanging the speed instruction as shown in FIG. 4B. Further, when thevalue counted by the relative position counter 4 has reached the stopoperation start position X2, the speed instruction generator 7 acommences a stop operation and changes the speed instruction.

As shown in FIG. 4D, changes appear in travel speed of the object 13such that the object 13 passes by the limit switch 6 (t0), such thatdeceleration is commenced when the value counted by the relativeposition counter 4 has reached the deceleration start position X1 (t1),and such that stop operation is started (t2) when the value counted bythe relative position counter 4 has reached the stop operation startposition X2.

In the sensorless controller 1 b of the synchronous motor of the secondembodiment, the deceleration start position X1 and the stop operationstart position X2 are set in advance. When the object has passed by thelimit switch 6 or when the value counted by the relative positioncounter 4 that has started counting operation has reached thedeceleration start position X1, deceleration operation is started. Whenthe counted value has reached the stop operation start position X2, stopoperation is commenced. Hence, a deceleration start limit switch and astop operation start limit switch, both being required to performpositioning control, can assume the form of a single limit switch. Areduction in the number of limit switches leads to a reduction in lengthof a wire extending from the limit switch to the controller, therebyfurther facilitating wiring operation.

A stop position can be readily adjusted by changing the decelerationstart position X1 and the stop operation start position X2. Hence, therecan be obviated a complicated operation, such as adjustment of a stopposition being performed by re-setting limit switches, which wouldotherwise be required.

Third Embodiment

FIG. 5 is a view showing the configuration of a sensorless controller 1c of a synchronous motor according to a third embodiment of theinvention. In the drawing, reference numerals 2, 4, and 10 designateelements which are identical with those shown in FIG. 1, and theirrepeated explanations are omitted. Reference numeral 1 c designates asensorless controller of a synchronous motor; 6 designates a limitswitch which outputs a reference position signal to the relativeposition counter 4; and 7 b designates a speed instruction generator forchanging a speed instruction in accordance with an output from therelative position counter 4. Reference symbols X1, X2, X3, and X4designate reference values set in advance on the speed instructiongenerator 7 b. Here, X1 designates a deceleration start position fornormal operation; X2 designates a stop operation start position fornormal operation; X3 designates a deceleration start position forreverse rotation; and X4 designates a stop operation start position forreverse rotation.

FIG. 6 is a view for describing operations of the sensorless controller1 c of the synchronous motor of the third embodiment of the invention,the operations differing because of a difference in rotationaldirection.

FIG. 6A shows an example configuration of a transfer apparatus; FIG. 6Bshows a speed instruction to be issued during forward rotation; FIG. 6Cshows an output from the relative position counter 4 during forwardrotation; FIG. 6D designates a speed achieved during forward rotation;FIG. 6E designates a speed instruction issued during reverse rotation;FIG. 6F designates an output from the relative position counter 4 duringreverse rotation; and FIG. 6G designates a speed achieved during reverserotation. In the drawings, reference numerals 14 a, 14 b designatestoppers.

The following description is provided while movement of an object fromleft to right in the drawing is taken as forward rotation operation andmovement of the same from right to left in the drawing is taken asreverse rotation operation.

During forward rotation operation, the speed instruction generator 7 bstarts deceleration by changing a speed instruction when the valuecounted by the relative position counter 4 has reached thepreviously-set deceleration start position X1 (t1). The speedinstruction generator 7 b commences a stop operation and changes thespeed instruction when the counted value has reached the stop operationstart position X2 (t2). During reverse rotation operation, when thevalue counted by the relative position counter 4 has reached apreviously-set deceleration start position X3 (t11), the speedinstruction generator 7 b starts deceleration by changing the speedinstruction. When the counted value has reached the stop operation startposition X4 (t12), the speed instruction generator 11 b commences a stopoperation and changes the speed instruction.

FIG. 4 of the second embodiment shows an example in which decelerationis started when the output from the relative position counter 4 hasreached the deceleration start position X1 and in which stop operationis started when the output has reached the stop operation start positionX2. However, when positioning is performed by changing a travelingdirection (e.g., when positioning to be performed during forwardrotation operation is changed to positioning to be performed duringreverse rotation operation), an operation for adjusting the position ofa limit switch for forward rotation operation and for reverse rotationoperation or an operation for changing the deceleration start positionX1 and the stop operation start position X2 is required. Moreover, whenpositioning is performed for forward rotation operation and for reverserotation operation, a limit switch for forward rotation operation andanother limit switch for reverse rotation operation are required.Moreover, depending on a traveling direction, a determination must berendered as to whether one of the limit switches is valid or invalid andwhether the remaining limit switch is invalid or valid.

However, the sensorless controller 1 c of the synchronous motor of thethird embodiment is provided with the deceleration start position X1 andthe stop operation start position X2 for forward rotation operation, andthe deceleration start position X3 and the stop operation start positionX4 for reverse rotation operation. The deceleration start position andthe stop operation start position can be individually set for forwardrotation operation and reverse rotation operation. Hence, positioningfor forward rotation operation and positioning for reverse rotationoperation can be carried out without involvement of an increase in thenumber of limit switches. Even when a traveling direction forpositioning is switched (when positioning to be performed for forwardrotation operation is switched to positioning to be performed forreverse rotation operation or vice versa), operation for adjusting limitswitches or operation for changing the deceleration start positions X1,X2 is obviated.

The foregoing description has described an example in which two pairs ofreference values to be previously set for the speed instructiongenerator 7 b are determined as the deceleration start position X1 andthe stop operation start position X2 for forward rotation operation andas the deceleration start position X3 and the stop operation startposition X4 for reverse rotation operation. A determination is made asto whether operation is forward rotation or reverse rotation. At thetime of forward rotation operation, the deceleration start position X1and the stop operation start position X2 are used. At the time ofreverse rotation operation, the deceleration start position X3 and thestop operation start position X4 are employed. A deceleration startposition and a stop operation start position, which are to be usedduring operation, may be selected during the course of movement of anobject in a single direction.

Fourth Embodiment

FIG. 7 is a view showing the configuration of a sensorless controller 1d of a synchronous motor according to a fourth embodiment of theinvention. In the drawing, reference numerals 2, 4, and 10 designateelements which are identical with those shown in FIG. 1, and theirrepeated explanations are omitted. Reference numeral 1 d designates asensorless controller of a synchronous motor; 7 c designates a speedinstruction generator for changing a speed instruction in accordancewith an output from the relative position counter 4; 15 designates alimit switch which outputs a reference position signal to the relativeposition counter 4; and 16 designates a limit switch for starting stopoperation. Here, X1 designates a reference value which is previously seton the speed instruction generator 7 c and corresponds to a distancefrom a location at which the limit switch 15 is to output a referenceposition signal to the deceleration start position.

FIG. 8 is a view for describing the operation of the sensorlesscontroller 1 d of the synchronous motor of the fourth embodiment of theinvention. FIG. 8A shows an example configuration of a transferapparatus; FIG. 8B shows a speed instruction; FIG. 8C shows an outputfrom the relative position counter 4; and FIG. 8D shows a speed.

In the drawing, reference numerals 10 through 13 and 14 a designateelements which are identical with those shown in FIG. 4, and theirrepeated explanations are omitted. Reference numeral id designates asensorless controller of a synchronous motor; 15 designates a limitswitch which outputs a reference position signal to the relativeposition counter 4; and 16 designates a stop operation start limitswitch.

Operation of the sensorless controller 1 d of the synchronous motoraccording to the fourth embodiment will now be described by reference toFIGS. 7 and 8.

When the synchronous motor is started up, the object 13 is movedrightward from the left end of FIG. 8A in accordance with a low speedinstruction f_(L).

At a point in time (t20) when the object 13 passes by the limit switch15 during low speed operation, the relative position counter 4 is reset,thereby starting counting operation. Moreover, at the point in time(t20) when the object 13 passes by the limit switch 15, the speedinstruction generator 7 c switches the instruction to a high speedinstruction f_(H).

When the value counted by the relative position counter 4 has reachedthe deceleration start position X1 during high speed operation (t21),the speed instruction generator 7 c switches the speed instruction tothe low speed instruction f_(L).

Deceleration is commenced, and at a point in time (t22) when the objectpasses by the limit switch 16 while traveling at a predetermined lowrotational speed, stop operation is started.

The second embodiment has described an embodiment in which the relativeposition counter 4 receives an output from the limit switch 6 as areference position signal during high speed operation, thereby startingcounting operation, in which, when a counted value has reached thedeceleration start position X1, the speed instruction generator 7 astarts deceleration operation, and in which, when the counted value hasreached the stop operation start position X2, a stop operation isstarted. The fourth embodiment is arranged such that the relativeposition counter 4 receives an output from the limit switch 15 as areference position signal during a low speed operation, thereby startingcounting operation. When a counted value has reached the decelerationstart position X1, the speed instruction generator 7 c startsdeceleration operation. At a point in time when the object has passed bythe stop operation start limit switch 16, stop operation is started.

In the fourth embodiment, a signal output from the limit switch 15 isread during a low speed operation, and hence occurrence of an error indeceleration start position, which would otherwise be caused by a delayin latching a signal, can be suppressed. Moreover, the object passes bythe stop operation start limit switch 16 during low speed operation, andhence the accuracy of stoppage can be improved further.

The forgoing embodiment has described an example in which thedeceleration start position X1 is used as an amount of movement to beset previously. Alternatively, the amount of movement to be used foreffecting the switch from low speed operation to high speed operationand the amount of movement to be used for starting stopping operationmay also be set and used in operation which would be performed when theobject passes by the limit switches 15, 16.

Fifth Embodiment

FIG. 9 is a view showing the configuration of a sensorless controller 1e of a synchronous motor according to a fifth embodiment of theinvention. In the drawing, reference numerals 2, 4, and 10 designateelements which are identical with those shown in FIG. 1, and theirrepeated explanations are omitted. Reference numeral 1 e designates asensorless controller of a synchronous motor; 7 d designates a speedinstruction generator for changing a speed instruction in accordancewith an output from the relative position counter 4; 15 designates alimit switch which outputs a reference position signal to the relativeposition counter 4; and 16 designates a limit switch.

FIG. 10 is a view for describing the operation of the sensorlesscontroller 1 e of the synchronous motor of the fifth embodiment of theinvention. FIG. 10A shows an example configuration of a transferapparatus; 10B shows a speed instruction; FIG. 10C shows an output fromthe relative position counter 4; and 10D shows a speed. In the drawing,reference numerals 10 through 13 and 14 a designate elements which areidentical with those shown in FIG. 4, and their repeated explanationsare omitted. Reference numeral 1 e designates a sensorless controller ofa synchronous motor; and 15, 16 designate limit switches. Referencesymbol f_(L) denotes a low rotational speed instruction; f_(M) denotes aspeed instruction for temporarily rendering a rotational speed lowerthan that achieved by a high rotational speed instruction; and f_(H)denotes a high rotational speed instruction.

Operation of the sensorless controller 1 d of the synchronous motoraccording to the fifth embodiment will now be described by reference toFIGS. 9 and 10.

When the synchronous motor is started up, the object 13 is movedrightward from the left end of FIG. 10A in accordance with a lowrotational speed instruction f_(L).

At a point in time (t20) when the object 13 passes by the limit switch15 during low speed operation before acceleration, the relative positioncounter 4 is reset, thereby starting counting operation. Moreover, atthe point in time (t20) when the object 13 passes by the limit switch15, the speed instruction generator 7 d switches the instruction to ahigh speed instruction f_(H).

When the value counted by the relative position counter 4 has reached anamount of movement X5 during high speed operation (t23), the speedinstruction generator 7 d temporarily switches the speed instruction tothe low speed instruction f_(M).

When the value counted by the relative position counter 4 has reached anamount of movement X6 during low speed operation (t24), the speedinstruction generator 7 d switches the speed instruction to the highspeed instruction f_(H).

When the value counted by the relative position counter 4 has reachedthe amount of movement X1 during high speed operation (t21), the speedinstruction generator 7 d switches the speed instruction to the lowspeed instruction f_(L).

Deceleration is commenced, and at a point in time (t22) when the objectpasses by the limit switch 16 while traveling at a predetermined lowrotational speed, stop operation is started.

The fifth embodiment is arranged so as to enable setting of theoperation change relative positions X5, X6. When the object 13 hasreached the previously-set operation change relative position X5, thespeed instruction is temporarily decreased. When the object 13 hasreached the previously-set operation change relative position X6, thespeed is again increased. Hence, when the sensorless controller is usedin conjunction with an operation pattern with a speed range includingmechanical resonance or in conjunction with an operation patternrequiring an inspection during the course of operation, a regionincluding mechanical resonance and a region corresponding to a period ofinspection are specified by X5, X6, whereby the object can be caused topass at low speed or actuated at a low speed which enables inspection.

Industrial Applicability

As mentioned above, a sensorless controller of a synchronous motoraccording to the invention enables positioning, at a predeterminedlocation, of a synchronous motor not having a position sensor.Therefore, the sensorless controller is suitable for use with all typesof motors, such as a brushless DC motor, an implanted magnet synchronousmotor (IPM), a switched reluctance motor (SRM), and a synchronousreluctance motor (SyRM), in applications in which positioning isperformed without use of a position sensor.

What is claimed is:
 1. A synchronous motor sensorless controller whichincludes a current sensor for detecting an electric current of asynchronous motor, a position-and-speed estimation device for computingan estimated speed of the synchronous motor and an estimated position ofa magnetic pole through use of the current output from the currentsensor, and a speed controller for controlling speed of the synchronousmotor through use of a speed instruction and the estimated speed; andwhich drives the synchronous motor without use of a rotational positionsensor, the controller comprising: reference position signal outputmeans for outputting a reference position signal serving as a standardfor positioning counting operation; a relative position counter whichacquires an estimated position of a magnetic pole from theposition-and-speed estimation device as a reference positionsimultaneously with resetting a summated value to zero when thereference position signal is input and which starts summation operation;and a speed instruction generator having a position controller whichperforms position control operation on the basis of a deviation betweenan instruction value pertaining to the amount of movement from thereference position and a summated value output as a relative positionfrom the relative position counter, the speed instruction generatoroutputting a speed instruction, wherein the speed instruction generatorenables setting of a deceleration start position and a stop operationstart position, starts deceleration operation when a summated valueoutput from the relative position counter as a relative position hasreached the deceleration start position, and starts stop operation whenthe summated value has reached the stop operation start position.
 2. Thesynchronous motor sensorless controller according to claim 1, whereinthe speed instruction generator can set at least two pairs, each pairformed from a deceleration start position and a stop operation startposition, enables selection of one to be used during operation from thedeceleration start position and the stop operation start position,starts deceleration when a summated value output from the relativeposition counter as a relative position has reached a selecteddeceleration start position, and starts stop operation when the summatedvalue has reached a selected stop operation start position.
 3. Asynchronous motor sensorless controller which includes a current sensorfor detecting an electric current of a synchronous motor, aposition-and-speed estimation device for computing an estimated speed ofthe synchronous motor and an estimated position of a magnetic polethrough use of the current output from the current sensor, and a speedcontroller for controlling speed of the synchronous motor through use ofa speed instruction and the estimated speed; and which drives thesynchronous motor without use of a rotational position sensor, thecontroller comprising: reference position signal output means foroutputting a reference position signal serving as a standard forpositioning counting operation; a relative position counter whichacquires an estimated position of a magnetic pole from theposition-and-speed estimation device simultaneously with resetting asummated value to zero when the reference position signal is input andwhich starts summation operation; stop operation start position signaloutput means for outputting a stop operation start position signal; anda speed instruction generator having a position controller whichperforms position control operation on the basis of a deviation betweenan instruction value pertaining to the amount of movement from thereference position and a summated value output as a relative positionfrom the relative position counter, the generator outputting a speedinstruction, wherein the speed instruction generator enables setting ofa changed speed instruction and a deceleration start position, changes aspeed instruction to the changed speed instruction when a referenceposition signal is input, starts deceleration operation when a summatedvalue outputted from the relative position counter as a relativeposition has reached the deceleration start position, and starts stopoperation when a stop operation start position signal is outputted fromthe stop operation start position signal output means.
 4. Thesynchronous motor sensorless controller according to claim 3, whereinthe speed instruction generator enables setting of a first changed speedinstruction, setting of a second changed speed instruction, setting of afirst operation change relative position, setting of a second operationchange relative position, and setting a deceleration start position;changes a speed instruction to the first changed speed instruction whenthe reference position signal is input; changes the speed instruction tothe second changed speed instruction when the summated value output fromthe relative position counter as a relative position has reached thefirst operation change relative position; changes the speed instructionto the first changed speed instruction when the summated value hasreached the second operation change relative position; startsdeceleration when a summated value output from the relative positioncounter as a relative position has reached the deceleration startposition; and starts stop operation when a stop operation start positionsignal is output from the stop operation start position signal outputmeans.